Suppression Of Superconductivity In The (La2.5-Xgd0.5+X)Caba3-Xsrx(Cu1-Yiny)(7)O-Z System Due To Hole Filling By In And Its Revival By Hole Doping With Ca

The structural and superconducting properties of single phase (La2.5-xGd0.5-x)CaBa3-xSrx(Cu1-yIny)(7)O-z. (LGCBS-CuIn) with 0 less than or equal to x less than or equal to 1 and 0 less than or equal toy less than or equal to 0.1 as well as Ca-substituted (La1.5-x'CaxGd1.5)CaBa2Sr(Cu0.90In0.10)O-z (LCGCBS-CuIn) with 0 less than or equal to x less than or equal to 0.6 compounds having triple-perovskite structure are investigated using X-ray diffraction, oxygen content, electrical resistivity and d.c. magnetization measurements. The effect of increasing simultaneous substitutions of Gd, Sr and In in LGCBSCuIn is to lower the carrier concentration and decrease T-c to zero at x = 1 and y 0.1, which is attributed to hole filling by In. This suppression in T, has been compensated for by appropriate hole doping with Ca, for instance in the oxide LCGCBSCuIn, the T-c increases from 0 K (x' = 0) to 68 K (x' = 0.6) due to the balance between the hole filling by In and hole doping by Ca. (C) 2001 Elsevier Science B.V. All rights reserved.